3
Reflex Arc
Components of a Reflex Arc
A.
Receptor
- reacts to a stimulus
B.
Afferent pathway (sensory neuron)
- conducts impulses to the CNS
C.
Interneuron
- consists of one or more synapses in the CNS (most are in the spine)
D.
Efferent pathway (motor neuron)
conducts impulses from CNS to effector.
E.
Effector
- muscle fibers (as in the Hamstring muscle) or glands responds by contracting or secreting a
product.
Spinal reflexes
- initiated and completed at the spinal cord level. Occur without the involvement of higher brain
centers.
Central Nervous System
•
Brain
o
Brain stem – medulla, pons, midbrain
o
Diencephalon – thalamus & hypothalamus
o
Cerebellem
o
Cerebrum
•
Spine
o
Spinal Cord
Meninges
Meninges are the three coverings around
the brain & spine and help cushion, protect,
and
nourish the brain and spinal cord.
•
dura mater is the most outer layer, very
tough
•
arachnoid mater is the middle layer and
adheres to the dura mater and has
weblike attachments to the innermost
layer, the pia mater
•
pia mater is very thin, transparent, but
tough, and covers the entire brain,
following it into all its crevices (sulci) and spinal cord
•
cerebrospinal fluid, which buffers, nourishes, and detoxifies the brain and spinal cord, flows through
the subarachnoid space, between the arachnoid mater and the pia mater